The Lusophone connection is the tale of how a famous west London footballing parish became a Portuguese enclave. When José Mourinho moved from Porto to Chelsea in 2004, bringing the defenders Ricardo Carvalho and Paulo Ferreira with him, a stream of fellow Lusophones followed as Portuguese became the club's second language, and the Blues began the most trophy-laden era in its history.

José Bosingwa, the Brazilian Alex and the naturalised Portuguese Deco, the coach Baltemar Brito and André Villas-Boas – as opposition scout, then later as manager – were just some who would turn a club headed by the English yeomen John Terry and Frank Lampard into Little Portugal.

Last year David Luiz, another Brazilian, arrived from Benfica; he is in line to face his former club when Roberto Di Matteo's resurgent side meet in the opening leg of their Champions League quarter-final in the Estádio da Luz in Lisbon on Tuesday.

Meanwhile, Eusébio's famous old club are moving in the opposite direction and it could be argued that Chelsea are now more Portuguese than Benfica. In the latter's previous Champions League outing, against Zenit St Petersburg, not a single Portuguese player featured, and this will be the case again this week.

Nelson Oliveira is the sole home-grown footballer to have started in the league for Benfica this season – once. Yet until 1979 when a Brazilian called Jorge Gomes was selected, the club had regulations forbidding any non-Portuguese pulling on the Eagles' red shirt.

Of his two spells as Benfica's head coach – 1982-84 and 1989-92 – Sven-Goran Eriksson recalls: "There were a lot of Portuguese players playing for us who played for the national team. But it was different at that time because none of the Portuguese players were playing outside of Portugal."

For the second leg of that last-16 tie against Zenit, Jorge Jesus's team was heavily South American: five Brazilians, an Argentinian, a Paraguayan and a Uruguayan were joined by two Spaniards and a Belgian. In all, Benfica's books show 15 Brazilians and 13 other South Americans. Eriksson says the reason for this shift is "probably because the best Portuguese players leave – there are a lot around Europe, in Russia, in Spain, France and so on and maybe it's easier for them to buy from South America. If you take Brazil, it is an old colony of Portugal."

Avram Grant, who managed Chelsea in 2007-08, between Mourinho and another Lusophone, Luiz Felipe Scolari, says Portuguese footballers have many attractive qualities: "They are both physical and technical, and can be a very good market because the players are similar to Brazilians – Portugal can bring any player they want from Brazil, and there is an influence there from players who are the best in the world.

"But they are European, so they also have the tactical side Brazil misses a bit. The typical Portuguese player has a sense of tactics but still the touch of the Brazilians. It's a good combination."

Eriksson says that assimilation is made easy by the closeness in culture between Portugal and the former colony: "The Portuguese are more or less similar to Brazilian players, yes, and also the language makes it very easy for them."

Before Mourinho's arrival began the Portuguese invasion, Chelsea previously had only two Lusophone players "It's quite a new thing, this connection," Rick Glanvill, Chelsea's official historian, says. "In the 1990s we had strong Italian links through Gianluca Vialli, Gianfranco Zola, Di Matteo, Claudio Ranieri, even Ruud Gullit [who played in Italy for most of his career].

"The only Portuguese-speaking players to play for Chelsea up to 2004 were Emerson Thome, who's Brazilian, and Filipe Oliveira. Oliveira was signed as a kid from Porto under Claudio Ranieri [Mourinho's predecessor] and made the first of only eight starts for us in 2002. There are a couple of other younger ones like Filipe Morais, who's now at Oldham, and [fellow quarter-finalists] Apoel's Nuno Morais, but they came later.

"José Mourinho arrived in 2004 and that's where the Portugal connection took off. Not only because he was such a huge figurehead and so successful, but because he surrounded himself with fellow countrymen on and off the pitch. Suddenly, with Riccy Carvalho, Paulo Ferreira, Tiago et al at Stamford Bridge, Portuguese was the second most common language in training. He also brought in André Villas-Boas and a bear of a man who spoke little English in assistant manager Baltemar Brito. There was a distinct cultural shift. Others we added included Deco, a converted Brazilian, Ricardo Quaresma and Maniche – briefly on loan – Alex, and Juliano Belletti [also Brazilians], Raul Meireles and Bosingwa."

Jorge Mendes, as the agent of Mourinho, Carvalho, Ferreira and Scolari, among others, was also a factor, becoming a key deal-maker in a pan-European exodus of Portugal's prime talent that has moved the national federation to order that the country's League Cup competition should showcase home players.

José Freitas, a senior football journalist with the Lisbon-based Record, says: "They have to play with two Portuguese players for at least 45 minutes because they want this competition to be one where the younger players can show themselves. Normally they do not have this opportunity in the main competitions to show what they can do.

"Benfica's Oliveira is a young guy of 20 who was a star for Portugal in last year's Under-20 World Cup when we lost the final to Brazil. He's a very good. But now he doesn't have many chances to play. He was on loan for two seasons and came back this year, and has only been playing 10, 15 minutes in matches. But in the group phase of the League Cup this kid played very well. Barcelona have been watching him all season but only come to watch him in these matches." Freitas does not expect Oliveira to start against Chelsea.

Asked how Benfica's fans feel about the paucity of Portuguese players in their team, Freitas adds: "It's the same everywhere. Since the Bosman rule there is no way you can stop this. Benfica once had in their own statutes that they could not play with foreign players. But supporters from any team just want their team to win."